The present invention relates to a thread cutting insert for use with an indexable tool comprising a flat wafer of cutting material of substantially triangular form, having a pair of opposed faces and a plurality of upstanding side walls extending therebetween. The juncture between the side walls defines a cutting corner that is placed substantially under an upper face. The cutting corner is provided with at least one cutting tip which upper surface defines a cutting surface. The cutting surface is provided with a positive first chipforming surface extending from a radiused nose part of the cutting tip to at least a half of a maximum feeding depth in a direction towards a second chipforming surface. The second chipforming surface is placed in the transition between the cutting surface and the upper face so that the first and the second chipforming surfaces cooperate to form and guide chips.
The chip obtained at chasing of threads with radial feeding is substantially V-shaped which form is very stiff and is therefore difficult to shape in a controlled way. A non-triangular thread cutting insert having a recessed cutting tip is previously known, but the chip obtained when machining a surface with such an insert will have a large radius of curvature which means chip entanglement and therefore risks for the operator, the work piece and the insert. A known thread cutting insert having a cutting corner placed under the upper face is provided with a chipforming area that, however, gives a chip with a large radius of curvature leading to the above-mentioned disadvantages. The form of the cutting tip of this insert gives a negative cutting course so that the insert will be subjected to large cutting forces.
The objects of the present invention is to provide a thread cutting insert with a shaping that solves the above-mentioned problems. The shape of the insert will give small cutting forces and a controlled chip removal at chasing of threads which means that the insert can be used for work pieces within a broad spectrum of materials and at varying machining data. These and other objects and advantages will become apparent with reference to the following detailed description in conjunction with the drawings in which: